Interlacing is a technique for processing animated images which is intended to reduce the bandwidth necessary for transmitting a sequence of images by only transmitting half of the information relating to each image.
More specifically, as a general rule, values are associated with the pixels in one out of two rows of pixels in the image. In this manner, a row of pixels with associated values for all its pixels succeeds a row of pixels to be assigned values, and the values to be assigned to the pixels must be determined. To process an interlaced image, it must be determined, on the basis of the values associated with the pixels in the rows of pixels in the image with values, the values to be associated with the pixels in the other rows of pixels in the image, or in other words the rows of pixels to be assigned values.
For this purpose, a deinterlacing algorithm is conventionally applied upon receipt of an interlaced image. One such algorithm determines the value to be associated with a pixel in a row to be assigned values, by using the average of the values associated with the neighboring pixels.
However, this type of algorithm is not suitable for a clean reconstruction of the contours of an object in the image.
Another known deinterlacing algorithm, known as ELA (for “Edge-based Line Average”), aims to improve the rendering of the contours of an interlaced image. An algorithm of this type is generally based on a partial path in the image to be processed via a search window. Such a search window is defined so as to be centered on a pixel for which an associated value must be determined. Then a direction is determined indicating the neighboring pixels within the search window which are the most appropriate for interpolation in order to determine a value to associate with the central pixel.
Thus by scanning a part of the image, there can be determined values to associate with all pixels of the image. U.S. Pat. No. 7,023,487 describes such an algorithm.
However, an image obtained after applying this type of algorithm is sometimes still of insufficient visual quality, particularly when the image represents contrasting areas which are relatively thin in shape, and also when a thin line is oriented in a direction close to the horizontal. One of the consequences for the viewer is a lack of continuity in the visual rendering of the image that is processed in this way.
In addition, such an algorithm is dependent on the size of the search window used to limit the direction of the contour reconstruction: the larger the search window, the greater the risk of an erroneous interpolation. Certain methods based on such search windows propose limiting the risks of erroneous interpolation, but these methods remain complex and difficult to implement.